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| -rw-r--r-- | gfx/wr/glsl-to-cxx/README.md | 21 |
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diff --git a/gfx/wr/glsl-to-cxx/README.md b/gfx/wr/glsl-to-cxx/README.md new file mode 100644 index 0000000000..54dcbc7d61 --- /dev/null +++ b/gfx/wr/glsl-to-cxx/README.md @@ -0,0 +1,21 @@ +A GLSL to C++ translator. + +Translates GLSL to vectorized C++. Intended for use with WebRender software backend. + +Architecture +------------ +GLSL code is parsed by the glsl crate. In hir.rs we traverse the resulting AST +and build a higher level representation by doing type checking and name +resolution. The resulting hir tree is traversed by lib.rs to output C++ code. + +The generated C++ code is 4x wider then the original glsl. i.e. a glsl 'float' +becomes a C++ 'Float' which is represented by a xmm register (a vector of 4 floats). +Likewise, a vec4 becomes a struct of 4 'Float's for a total of 4 xmm registers and +16 floating point values. + +Vector branching is flattened to non-branching code that unconditionally runs both +sides of the branch and combines the results with a mask based on the condition. + +The compiler also supports scalarization. Values that are known to be the same +across all vector lanes are translated to scalars instead of vectors. Branches on +scalars are translated as actual branches. |